[ietf-dkim] Are subdomains like parent domains?

[Arvel Hathcock]

>       How will it benefit phishers to use arbitrary sub-domains?

If the use of arbitrary sub-domains within an unsigned message can 
"get-around" an otherwise stricter receive-side filter then the benefit 
to phishers is obvious - their pay-load is all the more likely to be 
delivered.  Compliance with the current spec would not permit this to occur.

Arvel